The invention relates to a scraper chain for scraper chain conveyors, in particular, although not necessarily exclusively for mining conveyors, and especially center chain or double center chain conveyors, with interlinking vertical and horizontal chain links.
Whereas round link chains of standardized patterns have been used in the past as scraper chains for the scraper chain conveyors used mainly in underground longwall workings in coalmines, a transition was made some time ago, in response to the ever-increasing performance requirements for these conveyors, to the use of special link chains for the scraper chains. The vertical links of these chains are made flat along their parallel longitudinal limbs, so that the strength of the chain can be increased while keeping the height of the scraper chain low enough to enable it to be used on scraper chain conveyors commonly used in mining which are designed for lighter scraper chains. Such special scraper chains are described in DE 3234137 C2.
Based upon the abovementioned state of the art, DE 3704176 C2 has proposed a scraper chain in which the vertical links of the chain are likewise made with flattened limbs to reduce the height of the chain, while links of the conventional type, that is links with a constant circular cross-section all round, are used for the horizontal links of the chain. The vertical links in this scraper chain have a smaller pitch than the horizontal links, but the combined pitch of one vertical link and one horizontal link is equal to the combined pitch of two standard links of smaller size, so that, in the example envisaged, it is possible to substitute a size 42 chain of this pattern for a size 38 round link chain of the standard pattern without having to modify the diameters of the head and tail sprockets.
The invention takes as its starting-point the two abovementioned publications, whose disclosures are incorporated by reference into the description of the present invention. The principal object of the invention is to configure the scraper chain, formed as a link chain, in such a way as to optimize the scraper chain in terms of its overall dimensions and its carrying or pulling capacity whilst preserving the known advantageous features of the chain, and to enable the scraper chain to be used to advantage on scraper chain conveyors of very great conveying length, in particular on scraper chain conveyors for high-output longwall workings in underground mining.
The present invention provides a scraper chain for scraper chain conveyors, with interlinking vertical and horizontal chain links, the horizontal chain links having a constant circular cross-section all round, and the vertical links having in their curved nose-parts of round cross-section connecting longitudinal limbs of a cross-section which is flattened with respect to the round section, and is approximately oval in form, the horizontal cross-sectional axis of the said flattened cross-section having a width (L) which is greater than the diameter (d) of the circular cross-section of the horizontal links and of the nose-parts of the vertical links, and a height (H) which is smaller than the diameter (d) of the circular cross-section of the horizontal links and of the nose-parts of the vertical links, the scraper chain has a strength at least equal to that of a size 48 standard round link chain, the horizontal chain links having a circular cross-section all round, with a diameter of at least 48 mm; the horizontal links serving as scraper connection have a pitch which is at least 10% greater than the pitch (t1) of the vertical links, which is approximately equal to three times the diameter of the circular cross-section of the nose-parts of the vertical links, plus or minus 5 mm, and the outer width (B1) of the horizontal links is approximately 30% greater than the outer width (B2) of the vertical links.
With the invention it is possible to provide a scraper chain, formed as a link chain, for scraper chain conveyors which affords a very significant increase in pulling or carrying capacity over known scraper chains, whilst having particularly favourable overall dimensions, in particular a relatively low height, and in which moreover the horizontal links of the chain can be designed in respect of their pitch, and hence also their other dimensions, so that a reliable connection can be made between them and the scrapers. The dimensional proportions of the link chain according to the invention are selected and optimized so that it can be used on scraper chain conveyors as a scraper chain with a carrying capacity or strength at least equal to that of a size 48 standard round link chain in which the horizontal and vertical links are of similar form and each have a constant circular cross-section all around, or even of a round link chain of higher carrying capacity.
Particularly with regard to the strong and reliable connection of the scrapers, it is advantageous if the pitch of the horizontal chain links the vertical links having a pitch is greater by 15%xc2x11% than the pitch of the vertical links, which approximately corresponds to three times the diameter of the circular cross-section of the curved bow parts xc2x15 mm of the vertical links. Particular design features of a preferred embodiment scraper chain according to the invention are set forth in below for the case where the scraper chain is adapted in its carrying capacity or strength to a size 48 standard round link chain. The preferred dimensions are:
Pitch (t1) of horizontal links: 163 mmxc2x12 mm;
Pitch (t2) of horizontal links: 141 mmxc2x12 mm;
Diameter (d) of circular cross-section of horizontal links and of nose-parts. of vertical links 48 mmxc2x11 mm;
Outer width (B1) of horizontal links: 163 mm maximum;
Outer width (B2) of vertical links: 122 mm maximum;
Ratio of dimensions of horizontal and vertical cross-sectional axes (L/H) of flattened longitudinal legs of vertical links: 58:34=1.7xc2x10.1%.
A further advantage which may be gained with the invention is that the chain dimensions can be determined so that the head and tail sprockets for the scraper chain conveyor according to the invention have the same outer and/or reference diameter as sprockets for a size 42 standard round link chain; each sprocket is conveniently provided with seven teeth, as is known in itself.